Plant regulation of microbial enzyme production in situ

Soil extracellular enzymes regulate the rate at which complex organic forms of nitrogen (N) become bio-available. Much research has focused on the limitations to heterotrophic enzyme production via lab incubations, but little has been done to understand the limitations to enzyme production in situ. We created root and symbiotic mycelia exclusion treatments using mesh in-growth bags in the field to isolate the effect of roots and other portions of the microbial community on enzyme production. When fertilized with complex protein N we found increases in N-degrading enzyme concentrations only when root in-growth was allowed. No response was observed when complex N was added to root-free treatments. Expanding on economic rules of microbial element limitation theory developed from lab incubation data, we suggest this is due to active transport of labile carbon (C) from roots to associated microbial communities in root bags. Roots alleviate C-limitation of microbial enzyme synthesis, representing a trade off between plants and microbes- plant C for microbial derived N

Soil microbial community structure and allocation are critical drivers of ecosystem functioning

textThe functioning of terrestrial ecosystems is entirely dependent on the activity of autotrophic primary producers and microbial decomposers, and how they are affected by climate, mineralogy and anthropogenic change. Ecosystem ecology has classically focused on how allocation and community composition of plant primary producers may alter predictions of future ecosystem functioning in the face of environmental change. Little attention has been paid to allocation and community composition of microbial decomposers. The functioning of microbial decomposers has been considered implicitly, in the context of plant traits; primarily plant biomass chemistry. However, soil microbial communities represent a vast diversity of taxa spanning multiple kingdoms of life and an array of functional groups. It is not only likely, but probable that understanding ecological aspects of soil microbial community structure, activity, and allocation will fundamentally change how we understand and predict ecosystem function in the future. In chapters 1-3 of this dissertation, I explicitly considered how microbial activities varied based on microbial community structure and the resulting impacts for biogeochemical cycling. Specifically, in chapters 1 and 2, I manipulated the relative abundance of symbiotic root fungi to demonstrate that competition between symbionts and free-living decomposers for nitrogen slowed soil carbon cycling. In chapter 3, I scaled how nitrogen is partitioned between plants, mycorrhizas and free-living decomposer microbes to demonstrate how shifts in microbial community structure could explain how forests productivity is sustained over centuries. In chapter 4, I developed a microbial allocation framework that explicitly considers microbial resource environments. I demonstrated that past microbial allocation frameworks based on plant ecological mechanisms cannot explain allocation patterns of decomposer microbial life. Throughout this dissertation I attempt to put soil microbial life in an explicit ecological context that challenges current understanding of ecosystem process and will allow for deeper understanding and prediction of ecosystem functioning. Incorporating microbial community structure, allocation, and simple ecological mechanisms into models will improve the predictive power of ecosystem ecology.Ecology, Evolution and Behavio

Does elevated CO2 alter the way microbes behave underground?

Increase in carbon (C) emissions due to human activity is a major cause of global change, but it is unclear how trees obtain soil nutrients to sustain growth under these conditions. To better understand how root symbiotic fungi (ectomycorrhizal fungi, EMF) will react to an increase in atmospheric CO2 we’ve simulated such scenario using synthetic ecosystems where pine trees were planted with and without their EMF (Suillus cothurnatus), nitrogen (N), and soil carbon (C) additions, in elevated vs ambient CO2 growth chambers. By combining biogeochemical analysis with differential isotopic signatures of soil vs plant C, and a series of -omic approaches, we captured changes in soil nutrients, soil respiration, and microbial composition and activity. We found that elevated CO2 did not lead to a change in free living fungal community composition compared to ambient CO2. However, under elevated CO2, more gene modules of S. cothurnatus involved in C-N degradation pathways were impacted by soil C and N additions. In turn, under elevated CO2 and when the EMF was present, we found high enrichment of non-targeted metabolites. The release of CO2 from soil was highly dependent on soil C and N availability and shifted depending on plant C availability. Our results inform ecosystem models by showing that interactions between free living fungi and EMF are an important mechanism for determining ecosystem responses to elevated CO2. In turn, our results challenge the classic perspective that EMF solely absorb nutrients and water and give them to plants.Fil: Policelli, Nahuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Boston University; Estados UnidosFil: Averill, Colin. Eidgenossische Technische Hochschule zurich (eth Zurich);Fil: Brzostek, Edward. West Virginia University; Estados UnidosFil: Wang, Haihua. University of Florida; Estados UnidosFil: Liao, Hui-Ling. University of Florida; Estados UnidosFil: Verma, Vijay. University of Florida; Estados UnidosFil: Tappero, Ryan. Brookhaven National Laboratory; Estados UnidosFil: Vietorisz, Corinne. Boston University; Estados UnidosFil: Nash, Jake. University of Duke; Estados UnidosFil: Vilgalys, Rytas. University of Duke; Estados UnidosFil: Bhatnagar, Jennifer M.. Boston University; Estados UnidosESA 2023 - Meeting of the Ecological Society of AmericaPortlandEstados UnidosEcological Society of Americ

Global Imprint of Mycorrhizal Fungi on Whole-Plant Nutrient Economics

Mycorrhizal fungi are critical members of the plant microbiome, forming a symbiosis with the roots of most plants on Earth. Most plant species partner with either arbuscular or ectomycorrhizal fungi, and these symbioses are thought to represent plant adaptations to fast and slow soil nutrient cycling rates. This generates a second hypothesis, that arbuscular and ectomycorrhizal plant species traits complement and reinforce these fungal strategies, resulting in nutrient acquisitive vs. conservative plant trait profiles. Here we analyzed 17,764 species level trait observations from 2,940 woody plant species to show that mycorrhizal plants differ systematically in nitrogen and phosphorus economic traits. Differences were clearest in temperate latitudes, where ectomycorrhizal plant species are more nitrogen use- and phosphorus use-conservative than arbuscular mycorrhizal species. This difference is reflected in both aboveground and belowground plant traits and is robust to controlling for evolutionary history, nitrogen fixation ability, deciduousness, latitude, and species climate niche. Furthermore, mycorrhizal effects are large and frequently similar to or greater in magnitude than the influence of plant nitrogen fixation ability or deciduous vs. evergreen leaf habit. Ectomycorrhizal plants are also more nitrogen conservative than arbuscular plants in boreal and tropical ecosystems, although differences in phosphorus use are less apparent outside temperate latitudes. Our findings bolster current theories of ecosystems rooted in mycorrhizal ecology and support the hypothesis that plant mycorrhizal association is linked to the evolution of plant nutrient economic strategies

Angry opposition to government redress: when the structurally advantaged perceive themselves as relatively deprived

We examined (structurally advantaged) non-Aborigines' willingness for political action against government redress to (structurally disadvantaged) Aborigines in Australia. We found non-Aborigines opposed to government redress to be high in symbolic racism and to perceive their ingroup as deprived relative to Aborigines. However, only perceived relative deprivation was associated with feelings of group-based anger. In addition, consistent with relative deprivation and emotion theory, it was group-based anger that fully mediated a willingness for political action against government redress. Thus, the specific group-based emotion of anger explained why symbolic racism and relative deprivation promoted a willingness for political action against government redress to a structurally disadvantaged out-group. Theoretical and political implications are discussed

Ectomycorrhizal Plant-Fungal Co-invasions as Natural Experiments for Connecting Plant and Fungal Traits to Their Ecosystem Consequences

Introductions and invasions by fungi, especially pathogens and mycorrhizal fungi, are widespread and potentially highly consequential for native ecosystems, but may also offer opportunities for linking microbial traits to their ecosystem functions. In particular, treating ectomycorrhizal (EM) invasions, i.e., co-invasions by EM fungi and their EM host plants, as natural experiments may offer a powerful approach for testing how microbial traits influence ecosystem functions. Forests dominated by EM symbiosis have unique biogeochemistry whereby the secretions of EM plants and fungi affect carbon (C) and nutrient cycling; moreover, particular lineages of EM fungi have unique functional traits. EM invasions may therefore alter the biogeochemistry of the native ecosystems they invade, especially nitrogen (N) and C cycling. By identifying “response traits” that favor the success of fungi in introductions and invasions (e.g., spore dispersal and germination) and their correlations with “effect traits” (e.g., nutrient-cycling enzymes) that can alter N and C cycling (and affect other coupled elemental cycles), one may be able to predict the functional consequences for ecosystems of fungal invasions using biogeochemistry models that incorporate fungal traits. Here, we review what is already known about how EM fungal community composition, traits, and ecosystem functions differ between native and exotic populations, focusing on the example of EM fungi associated with species of Pinus introduced from the Northern into the Southern Hemisphere. We develop hypotheses on how effects of introduced and invasive EM fungi may depend on interactions between soil N availability in the exotic range and EM fungal traits. We discuss how such hypotheses could be tested by utilizing Pinus introductions and invasions as a model system, especially when combined with controlled laboratory experiments. Finally, we illustrate how ecosystem modeling can be used to link fungal traits to their consequences for ecosystem N and C cycling in the context of biological invasions, and we highlight exciting avenues for future directions in understanding EM invasion.Fil: Hoeksema, Jason D.. University of Mississippi; Estados UnidosFil: Averill, Colin. No especifíca;Fil: Bhatnagar, Jennifer M.. Boston University; Estados UnidosFil: Brzostek, Edward. West Virginia University; Estados UnidosFil: Buscardo, Erika. Universidade do Brasília; BrasilFil: Chen, Ko Hsuan. University of Florida; Estados UnidosFil: Liao, Hui Ling. University of Florida; Estados UnidosFil: Nagy, Laszlo. Universidade Estadual de Campinas; BrasilFil: Policelli, Nahuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Ridgeway, Joanna. West Virginia University; Estados UnidosFil: Rojas, J. Alejandro. University of Arkansas for Medical Sciences; Estados UnidosFil: Vilgalys, Rytas. University of Duke; Estados Unido

Assessing innovations for upscaling forest landscape restoration

There is an increasing urgency to implement large-scale ecosystem restoration to mitigate the biodiversity and climate crises. These efforts must be scaled up to counteract the widespread degradation of the world’s forests, although restoration costs can often limit their application. Thus, there is a pressing need to identify cost-effective approaches that catalyze landscape-scale ecological recovery. Here, we highlight seven assisted restoration innovations with demonstrated local-scale results that, once upscaled, hold promise to rapidly regenerate forests. We comprehensively assessed how each approach facilitated forest, woodland, and/or mangrove recovery across 143 studies. Our results reveal techniques with a marked ability to catalyze vegetation recovery compared to “business-as-usual” approaches. However, the context-dependent cost-benefit ratio and feasibility of applying particular approaches requires careful consideration. Our assessment emphasizes that we already have many of the tools necessary to drive the terrestrial restoration movement forward. It is time to implement and assess their efficacy at scale

Toward a Generalizable Framework of Disturbance Ecology Through Crowdsourced Science

© 2021 Graham, Averill, Bond-Lamberty, Knelman, Krause, Peralta, Shade, Smith, Cheng, Fanin, Freund, Garcia, Gibbons, Van Goethem, Guebila, Kemppinen, Nowicki, Pausas, Reed, Rocca, Sengupta, Sihi, Simonin, Słowiński, Spawn, Sutherland, Tonkin, Wisnoski, Zipper and Contributor Consortium.Disturbances fundamentally alter ecosystem functions, yet predicting their impacts remains a key scientific challenge. While the study of disturbances is ubiquitous across many ecological disciplines, there is no agreed-upon, cross-disciplinary foundation for discussing or quantifying the complexity of disturbances, and no consistent terminology or methodologies exist. This inconsistency presents an increasingly urgent challenge due to accelerating global change and the threat of interacting disturbances that can destabilize ecosystem responses. By harvesting the expertise of an interdisciplinary cohort of contributors spanning 42 institutions across 15 countries, we identified an essential limitation in disturbance ecology: the word ‘disturbance’ is used interchangeably to refer to both the events that cause, and the consequences of, ecological change, despite fundamental distinctions between the two meanings. In response, we developed a generalizable framework of ecosystem disturbances, providing a well-defined lexicon for understanding disturbances across perspectives and scales. The framework results from ideas that resonate across multiple scientific disciplines and provides a baseline standard to compare disturbances across fields. This framework can be supplemented by discipline-specific variables to provide maximum benefit to both inter- and intra-disciplinary research. To support future syntheses and meta-analyses of disturbance research, we also encourage researchers to be explicit in how they define disturbance drivers and impacts, and we recommend minimum reporting standards that are applicable regardless of scale. Finally, we discuss the primary factors we considered when developing a baseline framework and propose four future directions to advance our interdisciplinary understanding of disturbances and their social-ecological impacts: integrating across ecological scales, understanding disturbance interactions, establishing baselines and trajectories, and developing process-based models and ecological forecasting initiatives. Our experience through this process motivates us to encourage the wider scientific community to continue to explore new approaches for leveraging Open Science principles in generating creative and multidisciplinary ideas.This research was supported by the U.S. Department of Energy (DOE), Office of Biological and Environmental Research (BER), as part of Subsurface Biogeochemical Research Program’s Scientific Focus Area (SFA) at the Pacific Northwest National Laboratory (PNNL). PNNL is operated for DOE by Battelle under contract DE-AC06-76RLO 1830

Decadal changes in fire frequencies shift tree communities and functional traits

Global change has resulted in chronic shifts in fire regimes. Variability in the sensitivity of tree communities to multi-decadal changes in fire regimes is critical to anticipating shifts in ecosystem structure and function, yet remains poorly understood. Here, we address the overall effects of fire on tree communities and the factors controlling their sensitivity in 29 sites that experienced multi-decadal alterations in fire frequencies in savanna and forest ecosystems across tropical and temperate regions. Fire had a strong overall effect on tree communities, with an average fire frequency (one fire every three years) reducing stem density by 48% and basal area by 53% after 50 years, relative to unburned plots. The largest changes occurred in savanna ecosystems and in sites with strong wet seasons or strong dry seasons, pointing to fire characteristics and species composition as important. Analyses of functional traits highlighted the impact of fire-driven changes in soil nutrients because frequent burning favoured trees with low biomass nitrogen and phosphorus content, and with more efficient nitrogen acquisition through ectomycorrhizal symbioses. Taken together, the response of trees to altered fire frequencies depends both on climatic and vegetation determinants of fire behaviour and tree growth, and the coupling between fire-driven nutrient losses and plant traits

Integrated global assessment of the natural forest carbon potential

Forests are a substantial terrestrial carbon sink, but anthropogenic changes in land use and climate have considerably reduced the scale of this system 1. Remote-sensing estimates to quantify carbon losses from global forests 2–5 are characterized by considerable uncertainty and we lack a comprehensive ground-sourced evaluation to benchmark these estimates. Here we combine several ground-sourced 6 and satellite-derived approaches 2,7,8 to evaluate the scale of the global forest carbon potential outside agricultural and urban lands. Despite regional variation, the predictions demonstrated remarkable consistency at a global scale, with only a 12% difference between the ground-sourced and satellite-derived estimates. At present, global forest carbon storage is markedly under the natural potential, with a total deficit of 226 Gt (model range = 151–363 Gt) in areas with low human footprint. Most (61%, 139 Gt C) of this potential is in areas with existing forests, in which ecosystem protection can allow forests to recover to maturity. The remaining 39% (87 Gt C) of potential lies in regions in which forests have been removed or fragmented. Although forests cannot be a substitute for emissions reductions, our results support the idea 2,3,9 that the conservation, restoration and sustainable management of diverse forests offer valuable contributions to meeting global climate and biodiversity targets